Eat Up. You’ll Be Happier.

PARIS — MY father-in-law, an anthropologist, likes to talk about the time he ate dog penis. He was visiting a remote town in South Korea, and the mayor invited him to lunch. Once they’d finished the dog soup (not a big deal), a waitress carried out the boiled penis on a silver plate. The mayor cut it lengthwise with scissors, then served half to each of them.

Anthropologists are at the extreme end of what used to be a universal rule of hospitality: When a host offers you food, you eat it. It’s a show of trust, and a sign of belonging. Refuse his meal and you’re effectively rejecting him.

But as anyone who has recently tried to host a birthday party or a dinner in the English-speaking world knows, this rule no longer matters. Forget about dog penis; try offering visitors lasagna (it’s not vegan, not gluten-free, and it couldn’t have been cooked by a caveman).

Our increasingly choosy food habits are the subject of a French collection of academic essays, “Selective Eating: The Rise, Meaning and Sense of Personal Dietary Requirements,” which will be published in English next week. The editor, Claude Fischler, a social anthropologist, chose the topic after discovering that even anthropologists aren’t exempt: An Australian colleague said she had asked her Aboriginal subjects to accommodate her gluten-free diet, followed by choice, not by medical necessity.

Having lived in America and France, I’ve been on both sides of the picky-eating divide. I know it’s tiresome to hear about the paradoxically fabulous French eating habits. But it’s no accident that Unesco made the French gastronomic meal part of the “Intangible Cultural Heritage of Humanity.” It’s worth looking at how they cope with picky eaters.

When I arrived in Paris about a decade ago, I was a vegetarian (out of squeamishness) and on a low-carbohydrate diet. This had seemed reasonable in New York, but it baffled Parisians. Restaurants balked at making substitutions. Hostesses didn’t ask for my dietary requirements.

In one study, 68 percent of French adults said they force themselves to eat some of everything when they’re invited to someone’s house. A Parisian academic told me she became incensed when an American dinner guest requested a vegetarian meal. “Although she was extremely friendly and pleasant — never again!”

There are French vegetarians, too, of course. Lots of people here go on diets, including low-carbohydrate ones. Gluten-free pasta has appeared in the supermarket. But people are low-key about their by-choice eating schemes. The overarching conventional wisdom — what everyone from government experts to my French girlfriends take as articles of faith — is that restrictive diets generally don’t make you healthier or slimmer. Instead, it’s best to eat a variety of high-quality foods in moderation and pay attention to whether you’re hungry.

In “Selective Eating,” Jean-Denis Vigne, of France’s National Museum of Natural History, concludes that the Paleolithic diet is “more inspired by the myth of the noble savage than by the realities revealed by science,” and that humans are adaptable omnivores.

Choosy eating interferes with another key aspect of French mealtimes: the shared experience of food. In France, “eating does not have the sole purpose of nourishing the biological body but also and above all of nourishing the social bond,” writes the social psychologist Estelle Masson in “Selective Eating.”

This can seem excessively formal. When I invited some French families over to eat pizza and watch a soccer match on TV, they automatically assembled at my dining-room table for a sit-down meal. (I had foolishly envisioned eating pizza on the couch.)

We Anglophones have reasons for adopting strange diets. Increasingly, we live alone. We have an unprecedented choice of foods, and we’re not sure what’s in them, or whether they’re good for us. And we expect to customize practically everything: parenting, news, medicines, even our own faces.

Anyway, we’re not trying to have a shared experience of food. Mr. Fischler says that in his focus groups, Americans often described eating as part of an individual journey of self-discovery, in which each person tries to “find out over time and experience what my true nutritional self is, and satisfy it.”

But selective eating may not lead us to our best selves. Since I’ve lived in France, there’s been a march of studies pointing to the wisdom of what the French have been doing all along. Apparently it’s fine to eat some cheese, butter, chocolate and red meat; diets rarely work; and to lose weight, you should exercise more and eat less. Mr. Fischler is currently studying the health impact of eating together by looking at buffet tables at Club Med and the American “freshman 15.”

Eating among the French certainly affected me. After a few years here, I gave up most of my selective food habits. I still wouldn’t eat a dog’s penis, but I have tried oysters. It turns out that the best part of going with the food flow isn’t the health benefits or the cuisine, it’s the conversation. You can finally talk about something else.